EFFECTS OF DIETARY METHIONINE ON GROWTH, SERUM BIOCHEMICAL INDEXES, SERUM FREE AMINO ACID AND MUSCLE TEXTURE OF RICE FIELD EEL (MONOPTERUS ALBUS)

To investigate the effects of different forms of dietary methionine on rice field eel (Monopterus albus) initial weight (30±0.45) g, Crystalline methionine (C-Met), encapsulated methionine (E-Met), methionine hydroxyl analog calcium salt (MHA-Ca) and methionine hydroxy analogue (MHA), whose effective Met content was 2 g/kg, were added in basal diet to form five experimental diets for a 10-week trial. Results showed that methionine in all forms improved weight gain rate and protein efficiency ratio and decreased feed conversion rate of rice field eels with significant change in groups of MHA-Ca and MHA compared with control group (P<0.05). Methionine addition significantly improved activity of trypsin, the contents of serum bile acid, total cholesterol, total protein, urea nitrogen and ammonia, muscle gumminess and adhesiveness (P<0.05). MHA-Ca and MHA addition improved the contents of serum glucose and HDL, activity of intestinal amylase, hepatosomatic GOT, crude protein of whole fish, muscle hardness, springiness and chewiness significantly (P<0.05), but reduced hepatosomatic index and serum glutamic oxalacetic transaminase activity significantly (P<0.05). The peak level of serum methionine appeared at 6h in control group after feeding, but at 9h in C-Met and MHA-Ca groups, at 12h in E-Met group, and at 3h and 9h in MHA group. These results revealed that methionine addition improved growth performance of rice field eels with better effects for MHA-Ca and MHA.